Two stage varivolume hand pump



NOW 18, 1947. K D. GRUDIN 2,430,872

v TWO STAGE VARI-VOLUME HAND PUMP Filed May 4, 1944 @e /z 2z INVENTOR. .DAN/Ez. ec/o//v Patented Nov. 18, 1947 UNITED STATES PATENT OFFICE (Granted under the act of March 3, 1883, as

:amended April F30, 1928; 370 O. G. 757) 6 Claims.

The invention described herein may Ybe manufactured and vused by -or for "the Government Afor governmental purposes, without che payment to me Aof any royalty thereon.

This invention relates lto fluid pumps, having particular 'reference -t'o-a fpi-ston pumpoi variable piston-displacement. is -well -known with respect 'lto fluid pressure lactuated devices, there are `many 'applications wherein initial operation requires -the delivery .o'f `a large volume of fluid at a relatively low pressure but thereafter a much smaller yvolume of #fluid :at a relatively higher pressure.

'It-is therefore 7an object of this invention to provide, A-in lapump rof .this character, -means *for automatically reducing ithe piston rdisjgilacement forragiiven piston stroke whenthedischarge -pressure exceeds Ia predetermined value.

More :specicall-y, 'it iis an -object of Athe inventionj to provide a -pumpfof this-character with two pistonsone within thefother, Wlithmeans lto automatically retire son-e o'f the pistons fto =an inactive position to sreduce l.the volumetric discharge :per unit stroke' when the pressure being pumped against rises itc a :predetermined height.

:other `.dialects and advantages will be evident as the invention is described kin greater detail, reference :being Ehad 'to the `drawing, wherein:

Fig.. 1'1 bis :a wew .-of :my improved pump, partly in zeleyationand Apartly in vertical-'axial section, showing :the mechanism .as 'it appears `when `set for pumping .a l'large *volume AVagainst a relatively low 'back pressure.

lFig. 2 fis :a View similar to`Fig. 1 `except that the layer piston has ,automatically -lmoved to its retired -position fand the .device is -now arranged for pumping 1a smaller -milurne against a relatively higher back ipressure.

Eig. .3 shows .aidetailef "the locking means which holds the larger piston in the operative position shown in Fig. 1.

`Referringmorerparticularlyteilig. `-1, `,the pump body Acomprises ya fcylinder Ill fprovided with a front :head I2 which houses the valves, Land a rear @head I4 which -carries the pump handle. Heads ft2 -a-nd If4 lare internally :threaded to `t external threads Miron the cylinder, the head I2 being ,provided `withza 'pressure seal I8, `and the head -M with .an inturrredflip 20 which-abuts :the cylinder lend ywhen the lhead is screwed up tight.

.Slidab-lyiltted Ito' the =bore of the cylinder Ill is alarge ,piston 12,2 havlinga `=hub 2'4, the piston being `.externally grooved 'for la seal i215, and the hub being internally 'grooved or ia seal "28. The lar-ge piston .-22 has :a lbfore 12191which is -of a some- 2 what larger diameter than `the'bore ofthe hub'Z'fl, the Alarger 'bore 29 having an internal annular ycavity whichzis wide enough to receive several circumferentially spaced locking balls 32 when they are pushed radially outward into the groove.

`Slidably tted to the bore of the hub 24 is a smallpiston 34 which, inthe embodimentvshown, is 'of substantially half `the diameter of the large piston, although any other relative proportion between the large and small pistons may be employed which 'the pumping requirements indicate as desirable. The'fron'tend of the small .piston'il carries an external annular rib 36 over which the bore '29 of the ,piston 22 Amay pass freely. The rearward face of the annular rib '36 is beveled as at 3l, the 'bore 29 of the large piston 22 being correspondingly 'beveled to provide camming .surfaces for a purpose which will hereinafter appear. The forward face of the external rib 35 s ,in the same planeas the rearward face of the internal-annular cavity 30,.

The interior .of the small piston34, at the .rearward end, has a chamber `38 for the spring 4I), and, at the forward end, is bored at 42 and counterbored at 44 for the unlocking plunger 46, the bore vl2 being provided with .an internal annular groove for -the seal 48.

The rear portion 50, middle portion 52, and front portion l54 of `'the unlocking plunger i6 are slidable respectively in the bores 4.2, 44 and 29, the rear face ofthe front portion 54 being beveled at 56 vto provide `another camming surface, fthe purpose of which will be later explained.

The extreme rearend of the .part 50 is threaded for the nut 58. Adjustment of nut 58 snugs up the beveled cam surface 56 to the locking balls 32. The forward end of the spring in reacts against the nut 58 and holds it against its shoulder in the small piston 34 While `the rearward end of the spring reacts against the nut 60. Adjustment of the nut 6I] may be made to vary the stress of the spring 4I). Adjustment vof the spring 40 varies the degree of back pressure at which the device will operate to retire the larger piston 22, A single-leaf spring 62 is provided for each locking ball 32 for urging the ball radially inward against the middle portion V52 of the locking plunger 46. y

A suction valve'fl `and a discharge valve 66 are built into the front head I2 and are held on their respective seats by the springs 68 and lil. A pump handle v'I2 is iulcrumed on the bracket portion 'I4 ofthe rear head I4fby a pin 16, a link 13, and pins 6U and 82 being employed to connect the pump handle to the ears 84 on the rear end of the small piston 34. The device shown in its normal unoperated position in Fig. l operates as follows:

Where the operation of a liuid actuated device requires a relatively low pressure in the beginning, the two pistons 22 and 34 will be locked together in the relative position shown in Fig. l. Each full stroke of the pump handle 'l2 will therefore displace a volume of fluid equal to the area of the bore of the cylinder Il) times the stroke, this volume being drawn through the suction Valve 64 and forced through the discharge valve 63 in the manner of any ordinary piston pump.

When the back pressure against which the pump must discharge rises to such a height that the locking plunger 45 is forced rearward on the pressure stroke, against the resistance of the spring 40, the locking balls 32 are forced radially outward by the cammingr surface 53 on the annular rib 54, into the cavity 30, outward movement of the balls being opposed by the springs 62, whereby the balls 32 pass over the annular rib 36 and the large piston 22 is thereafter free to slide rearwardly on the small piston 34. Y

If the unlocking mechanism should operate to unlock the large piston when the pistons are in the forward position shown in Fig. 1, the fluid drawn in through the suction valve 64 in the next two or three strokes of the pump may be required to move the large piston 22 to its fully retired position shown in Fig. 2 where. further rearward movement has been arrested by the inturned lip 20. While there is some tendency on the suction stroke to draw the large piston forward from its retired position, Fig. 2, the friction of the seal 26 is great enough to hold the piston against the equivalent suction head within the cylinder on the suction stroke.

Thereafter pumping may continue with the small piston 34 only, whereby the same expenditure of energy applied to the pump handle 12 will move fluid through the discharge valve 66 against four times the back pressure possible when both pistons were operative.

When it again becomes desirable to pump the 3 large volume against the lesser back pressure, the large piston 22 may be operatively reconnected to the small piston 34 by bringing the pump handle l2 to the extreme rearward position, which will cause the cam surface 31 on the annular rib 36 to A raise the locking balls 32 enough to let them pass over the rib to their locked position shown in Fig. 1. The two pistons will thereafter operate coincidentally.

Having described my invention, I claim:

1. In a pump of the character described, a pump body, a piston slidable within said pump body, a second piston slidable within said pump body, means to reciprocate one of said pistons, a lock for connecting said rst piston to said second piston for simultaneous reciprocation, and means associated with said pistons automatically responsive to a predetermined discharge pressure within said pump body to release said lock to thereby disconnect said rst piston from said seco-nd piston for independent reciprocation.

2. In a pump of the character described, a pump cylinder, a piston slidable in said cylinder, a second piston slidable within the rst piston, means to reciprocate one of said pistons, a lock carried by one of said pistons and operative to engage the other of said pistons for connecting said pistons for simultaneous reciprocation, and means associated with the said other of said pistons automatically responsive to a predetermined discharge pressure within said cylinder to release said lock from engagement with the said other of said pistons.

3. In a pump of the character described. a Gylinder, a piston having a concentric bore reciprocable in said cylinder, a second piston having a bore, said second piston being reciprocable in the bore of said rst piston, means to reciprocate one of said pistons, a radially movable lock for connecting said pistons for unitary reciprocation, an unlocking plunger movable axially in the bore of said second piston by a predetermined discharge pressure within said cylinder, and means carried on said unlocking plunger automatically operative upon axial movement of said unlocking plunger in response to said discharge pressure to move said lock radially to unlock said lock.

4. In a pump of the character described, a hollow cylinder with one end closed, a hollow piston with a concentric bore reciprocable in said cylinder, a second bored piston reciprocable in the bore of the rst piston, means to reciprocate one of said pistons, a lock normally connecting said pistons for unitary reciprocation, an unlocking plunger slidable in the bore of the second piston, a spring in said second piston for holding said plunger in the unoperated positions, said spring being yieldable at a'predetermined pressure in the closed end of said cylinder to move axially, and means carried on said plunger for unlocking said lock.

5. In a pump of the character described, a pump cylinder with one end closed, a pump piston slidable in said cylinder, a second pump piston, the first said piston being bored to slidably receive the second said piston, an unlocking plunger slidable in said second piston, the said second piston being bored to slidably receive said unlocking plunger, said plunger normally extending from the front end of said bore, a locking ball, the first said piston having a cavity into which said locking ball may move from the bore radially outward, the rear face of said cavity and the front face of the second said piston being in the same right plane, a spring urging said ball radially inward against said unlocking plunger, said plunger being of such diameter that when it arrests radially inward movement of said ball substantially half of said ball will extend beyond the inner extremity of said cavity, cam means carried on said plunger normally resting against the forward side of said locking ball but adapted upon rearward movement of said plunger to move said ball radially outward to a position wholly within said cavity, a resilient means tensioned to hold said plunger in its forward position but adapted to be overcome to allow said plunger to move rearwardly by a predetermined pressure in said closed end, and means to reciprocate the second said piston.

6. In a reciprocatory piston pump, the improvement which comprises two pistons, the second axially slidable within the first, an unlocking plunger axially slidable within the second piston, the forward face of the first piston and the forward face of the plunger extending beyond the forward face of the second piston, a spring urging said plunger forwardly, a stop limiting said forward movement, an internal annular groove in said first piston, the rearward face of said groove being in the same plane as the forward face of the second piston, a ball in said groove, a spring urging said ball radially inward against said plunger, said plunger being of such diameter that half of the ball protrudes from said groove, an annular rib around the front end of said plunger, a second annular rib around the front end of the second piston, the rearward face of the rst said rib being formed into a cam surface operative when moved rearwardly against the ball to move said ball radially outward whereby it may pass rearwardly over the second said annular rib, and tl'ie rearward face of the second said annular rib being formed into a cam surface operative when moved rearwardly against the ball to move the ball radially outward, whereby it may pass forwardly over the second said annular rib.

DANIEL GRUDIN.

REFERENCES CITED The following references are of reeord in the file of this patent:

Number Number UNITED STATES PATENTS Name Date Lindsay May 1, 1860 Stucky Oct. 15, 1878 Ten Eyck Mar. 1, 1904 Fraser Apr. 23, 1918 McNab 1 Nov. 11, 1930 McNab Oct. 27, 1931 McGee June 15, 1937 FOREIGN PATENTS Country Date Great Britain 1885 

